To gain added information regarding age related changes in CNS functioning, a variety of electrophysiological and behavioral measures are being obtained from 20 normal human subjects in each of three age ranges: 20-30, 40-50, and 60-70 years. Subjects in the oldest group have been screened by a neurological examination. Studies are included which are designed to measure electrophysiological correlates of age related changes in inhibitory deficits, speed and efficiency of central processing, learning, attention and habituation. While the primary electrophysiological measure is the averaged visually evoked response (VER), extensive analyses will be made of the single trial evoked responses (STRs) from which VERs are averaged. The STRs will provide information regarding age-related variability in CNS responsivity. In addition power spectral analysis of nonstimulated EEG will be obtained for each subject and related to amplitude and wave form of visually evoked responses. Behavioral tests include: Spiral aftereffect, Complex reaction time, Graham-Kendall Memory-for-Designs, speed of tapping, critical flicker fusion and a measure of the ability to accurately estimate the number of dots briefly projected on a screen.